A vaccine, like any medicine, could possibly cause serious problems, such as severe allergic reactions. The risk of a vaccine causing serious harm, or death, is extremely small.
Serious problems from inactivated influenza vaccine are very rare. The viruses in inactivated influenza vaccine have been killed, so you cannot get influenza from the vaccine.
Mild Problems
soreness, redness, or swelling where the shot was given
hoarseness; sore, red or itchy eyes; cough
fever
aches
headache
itching
fatigue
If these problems occur, they usually begin soon after the shot and last 1-2 days.
Moderate Problems
Young children who get inactivated flu vaccine and pnemococcal vaccine (PCV13) at the same time appear to be at increased risk for seizures caused by fever. Ask your doctor for more information.
Tell your doctor if a child who is getting flu vaccine has ever had a seizure.
Severe Problems
Life-threatening allergic reactions from vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the shot.
In 1976, a type of inactivated influenza (swine flu) vaccine was associated with Guillain-Barré Syndrome (GBS). Since then, flu vaccines have not been clearly linked to GBS. However, if there is a risk of GBS from current flu vaccines, it would be no more than 1 or 2 cases per million people vaccinated. This is much lower than the risk of severe influenza, which can be prevented by vaccination.
The safety of vaccines is always being monitored. For more information, visit: Vaccine Safety Monitoring and Vaccine Safety Activities.
One brand of inactivated flu vaccine, called Afluria, should not be given to children 8 years of age or younger, except in special circumstances. A related vaccine was associated with fevers and fever-related seizures in young children in Australia. Your doctor can give you more information.
This information was taken directly from the Inactivated Influenza VIS [PDF - 269 KB]
(This information taken from Inactivated Influenza VIS dated 7/2/12. If the actual VIS is more recent than this date, the information on this page needs to be updated.)